This invention relates to towed vehicles and more particularly to a compact system for deploying and retrieving towed decoys so that they can be redeployed multiple times.
As will be appreciated, aerial towed objects are used for a variety of purposes, including decoys, testing, and scientific investigations. In one embodiment, these decoys are used to draw various types of guided weapons away from an aircraft that the weapons are intended to destroy. As will be appreciated, these towed targets and decoys contain various types of electronic circuits to create an apparent target to a weapon to attract the weapon to the decoy rather than the aircraft. One active electronic device used in a decoy is a traveling wave tube amplifier to which high voltages must be applied to power the traveling wave tube. Additionally, other controls for the traveling wave tube or other electronics in the towed device are transmitted in one embodiment along a fiber optic transmission line, which is both frangible and fragile.
In the typical military operation, the decoys are sacrificed, meaning that the cables that attach the decoy to the deployment canister are severed after the decoy has been used.
The practice of cutting decoys after use and using them as an expendable commodity causes multiple problems. As a result it becomes important to be able to recover the towed vehicle itself, mainly because of the cost of the towed vehicle, as well as the fact that replacing towed vehicles often is difficult due to the long lead times in the manufacturing process and provision of such decoys.
For instance, typically a towed countermeasure decoy may cost as much as $50,000 per decoy round. As many as eight decoys per sortie or mission can be deployed and as such, assuming 400 sorties per month, then the total expense of deploying expendable decoys is quite large, making the cost for the protection of the aircraft that employ these decoys excessive. Moreover, in a wartime setting, the decoy cannot be manufactured quickly enough. So bad is the situation that it may be necessary to scrounge decoys from the battlefield where they fall for reuse.
There is therefore a necessity for being able to deploy a towed decoy in such a manner that it can be powered and controlled during the countermeasure operation, while at the same time, being able to be retrieved and reused again.
In the past, attempts to deploy such decoys in a rapid manner have included a spinning reel-like spindle payout system in which the decoy is paid out behind the aircraft without the ability to winch it back in.
It will be appreciated that priorly the only airborne towed devices that were winched into the aircraft after use were sonobuoys or towed instruments deployed from helicopters in which the winching systems themselves occupied inordinate amounts of space. As such, these devices were unsuitable for combat aircraft due to the current volume constraints on tactical aircraft. Thus, due to both the size and problems with slowly winching out a towed vehicle, no such winching systems were applied to the towed decoys for combat.
It is noted that sonobuoys and pod-mounted countermeasures were typically carried in an equipment pod the size of an MK-84 aerial bomb or the ALQ-164 type electronics counter-measures pod. What will be appreciated is that these pods are exceptionally large and preclude, for instance, the carrying of armaments in the position where the pod is located. Thus the payload of any attack aircraft would be severely limited if unwieldy winching systems such as associated with sonobuoys along with the associated housing were used to deploy normal decoy rounds. Note that prior art winding systems occupied a space many times the size of the normal decoy round.
By way of further background, the types of decoys involved have included devices which countermeasure infrared guided and radar guided missiles that pose the primary threats to military aircraft engaged in a combat environment. It will be appreciated that these missiles use their radar guidance systems to get within striking distance of the aircraft, thereby substantially increasing their probability that the IR system on the missile will be able to lock onto the target.
Current military aircraft are particularly vulnerable to attack from IR-guided surface-to-air and air-to-air missiles. Statistical data of aircraft losses in hostile actions since 1980 show that almost 90 percent of these losses have been the result of IR-guided missile attacks. As a result, the ability to deploy and then recover decoys that can counter-measure the IR guidance systems on these missiles is of great value to protect aircraft during combat situations. As mentioned above, the IR-guided system initially utilizes radar guidance and then switches over to IR guidance as they come into closer proximity to the target. If one can counter-measure the radar system, then the IR portion can never lock onto the particular infrared target. To do this, the missile is deflected away by generating a signal that causes the radar guidance system in the missile to think that the target is actually elsewhere than it actually is.
In the past, the ALE-50 Towed Decoy system currently in the inventory of the US Armed Forces includes a decoy round in a canister and a reel payout mechanism. When the decoy has served its purpose, it is cut loose and the ALE-50 decoy is lost.
Moreover, the same scenario is true for the more modern ALE-55, or in fact, any type of expendable towed vehicle.
In summary, prior art decoys were intended to be sacrificed and the towline was typically cut at the aircraft at the end of flight or mission. Thus, these systems did not contemplate the winching in or reeling in of the decoy. The reason is because these decoys needed to be rapidly deployed. One rapid deployment method included a spindle that paid out the towline in much the same way as a spinning reel pays out fishing line. Although spinning reel-like techniques have existed for fishing, in the area of rapidly deployed decoys they were not used to winch decoys. Also, the spindles themselves were not necessarily driven.
As will be appreciated, there are a number of U.S. patents that in general cover towed vehicle deployment, such as U.S. Pat. Nos. 5,836,535; 5,603,470; 5,605,306; 5,570,854; 5,501,411; 5,333,814; 5,094,405; 5,102,063; 5,136,295; 4,808,999; 4,978,086; 5,029,773; 5,020,742; 3,987,746 and 5,014,997, all incorporated by reference herein. In none of these patents is the subject retrievable system shown or taught.
In order to deploy, retrieve and reuse towed decoys, in the subject system, the decoy is housed in a canister with a towline wound around a level winding winching system, which during the deployment of the decoy, winches out the decoy at a moderately high speed. In the subject system, both the high voltage electrical signals to the traveling wave tube within the decoy and the controls for the countermeasure system carried by the decoy are transmitted over an electro-optic cable into which is embedded a length of high voltage tension line to be able to power the traveling wave tube. In one embodiment, there are five lines that carry a voltage, including three at high voltage, one at low voltage and a ground. The signals to control the countermeasure device within the decoy are carried by the relatively fragile fiber optic cable, which, in one embodiment, is connected to drive circuitry through a fiber optic rotary joint, such that the decoy can be winched out and retrieved with the signals passing through the center shaft of the level winding winching system. Additionally, high voltage slip rings are utilized along with the fiber optic rotary joint such that all the necessary signals and voltages can be applied to the decoy without any twisting of lines. It will be appreciated that in winching systems where the same line is utilized which winches the decoy in and out and is utilized for signal transmission, twisting inevitably occurs, which would damage both the fiber optic cable and the high voltage transmission lines.
In the past when towed decoys were deployed in the so-called spinning reel type of environment, the amount of twist imparted to the cable itself was not sufficient to cause damage to the cables.
However, when considering a fully-winched system, it is important to consider how it is that the cables can be deployed without fracture or injury, thus to permit multiple deployments. As part of the subject invention, the feeding of the line from and to the level winding winching system is accomplished with means to prevent backlash and jamming of the line during the retrieval process, as well as damage to the line during deployment. Secondly, the tension of the line during the retrieval process is continuously monitored so that excessive loads are avoided.
Central to the subject invention is a telescoping or extensible cradle or saddle which is extended after deployment of the decoy and which is utilized to capture the retrieved decoy as it is reeled in. After the decoy has reached its captured position, the entire telescoping assembly is retracted such that the decoy and the assembly are retracted into the canister from which the decoy can be redeployed.
The result is a decoy deployment system which can be used multiple times, due to the fact that the deployed decoy is captured and stored in the original canister. Secondly, multiple deployments of the decoy do not result in damage to the single towing line such that through the utilization of the fiber optic rotary joint, high voltage slip rings and the level winder traverse mechanism, decoys can be carried on an aircraft in a space that is one-tenth the size of prior equipment pods and at the same time permits the decoy to be deployed and redeployed even during the same mission.
In summary, a decoy deployment and retrieval system includes an extensible boom and corresponding cradle or saddle for use in the retrieval of the towed decoy such that upon retrieval the extensible boom with its decoy captured in the cradle is retracted into a chamber so that the decoy can be deployed over and over again. In one embodiment, the decoy is both towed by and controlled over a fiber optic line in which a load cell is used to detect tension on the line to prevent damage, and a fiber optic rotary joint is utilized along with high voltage slip rings to permit electrical and optical coupling without backlash, fouling, or damage to the line.